A friction clutch of this type is known from German Auslegeschrift No. 16 25 849, first published on Aug. 20, 1970, in which the spring for the safety clutch is arranged in the power flow - viewed from the clutch pack - behind the gear which must be coupled, so that when the safety clutch becomes effective, the gear must move. Thus the safety clutch is burdened with the mass of the gear, which can lead to difficulties during shifting, which are noticed externally by a chatter noise during shifting.
These disadvantages are overcome, if the masses in the power flow are arranged behind the spring first published Dec. 6, 1973 (German Patentschrift No. 2 225 096), so that the initial tension force of the spring is being influenced by as little mass as possible, in particular not by the mass of the movable gear. For certain cases of use, primarily if only small powers are to be transmitted, the installed length of this construction is relatively great. The transmission volume and thus the transmission price can therewith not be reduced proportionally with the output in the lower power range.
Other types of known structures are disclosed in U.S. Pat. Nos. 3,203,525 and 3,703,226.
Therefore, the basic purpose of the invention is to provide a friction clutch of the above-described type, which has at a relatively small assembled length still only small masses which act onto the spring.
This purpose is inventively attained by the carrier sleeve being mounted axially movably on the shaft and the supporting spring being arranged on the side of the carrier sleeve remote from the clutch friction surfaces, between the carrier sleeve and the shaft or between the carrier sleeve and a part which is fixedly connected to the shaft.
To increase the operating safety, two stops are arranged as is actually known, to limit the axial movement of the friction ring in direction of the clutch engagement of which stops the first is effective until the torque is exceeded and the second during an exceeding of the maximum permissible torque.
A preferable development of the invention is achieved, when the second stop is arranged acting in peripheral direction. Stops which act in peripheral direction are known. The friction ring which is supported through rolling elements on the guide sleeve carries out a helical movement, that is, a movement in both the axial direction and the peripheral direction. The stop which acts in peripheral direction prevents a jamming of the rolling elements or of the friction ring at high torque. The invention becomes particularly advantageous with an arrangement of the spring in the annular space which is formed by the carrier sleeve, shaft, gear and clutch element to thereby provide a compact solution.